Field of the Invention
The invention relates to a burner for fluidic fuels, in particular for use in a gas-turbine plant.
A burner for fluidic fuels, which is used in particular in a gas-turbine plant, has been disclosed by German Published, Non-Prosecuted Patent Application DE 42 12 810 A1. It is apparent from that publication that air is fed through an annular air-feed-duct system and fuel is fed through a further annular-duct system to the combustion. In that case, fuel is injected from the fuel duct into the air duct, either directly or from swirl blades constructed as hollow blades.
The intention is thus to achieve, inter alia, a homogeneous mixing of fuel and air as far as possible in order to achieve combustion having a low concentration of nitrous oxides. It is an essential requirement for combustion, in particular for combustion in the gas-turbine plant of a power station, to achieve as low a production of nitrous oxides as possible, for reasons of environmental protection and corresponding statutory guidelines for pollutant emissions. The formation of nitrous oxides increases exponentially with the flame temperature of the combustion. If there is inhomogeneous mixing of fuel and air, a certain distribution of the flame temperatures in the combustion region results. In accordance with that exponential connection between nitrous-oxide formation and flame temperature, the quantity of nitrous oxides being formed is substantially determined by the maximum temperatures of such a distribution. Accordingly, the combustion of a homogeneous fuel/air mixture, at the same average flame temperature, achieves a lower nitrous-oxide discharge than the combustion of an inhomogenous mixture. In the case of the burner structure of the publication cited, spatially effective mixing of air and fuel is achieved.
European Patent Application 0 561 591 A2 discloses a rotation cascade for generating a turbulent flow for use in a burner, in particular in a premix burner of a gas turbine. The rotation cascade serves to generate two concentric, contra-rotating flows so that, during partial-load operation of the gas-turbine plant, a reduced fuel quantity is burned in an inner flow in an air quantity reduced by splitting up into two flows and thus stable combustion can also be maintained during partial-load operation. Furthermore, the rotation cascade generates backflow zones which directly adjoin the rotation cascade and constitute combustion zones for stable combustion.
European Patent Application 0 619 134 A1 discloses a mixing chamber for mixing substances, e.g. in chemistry and in the production of foodstuffs or pharmaceuticals. The substances to be mixed are subjected to vorticity in separate ducts by a vortex generator and then brought together. The vortex generator is formed by deflecting elements constructed as elongated half pyramids.
A method and a device for the combustion of a free-flowing fuel, in particular in the burner of a gas turbine, are described in German Published, Non-Prosecuted Patent Application DE 44 15 916 A1. A turbulence-generating configuration is inserted in the air duct of the burner, so that combustion air is subjected to vorticity. Fuel is admitted to the vortical combustion air, so that an especially effective intermixing of fuel and combustion air is obtained. The vorticity is achieved by a number of obtuse flow obstacles, in particular by rods or discs. German Published, Non-Prosecuted Patent Application DE 41 23 161 A1 discloses a vortex element designated as a static mixer. It has a multiplicity of deflecting elements, which are small relative to the diameter of a pipe line or a flow duct in which it can be inserted and are inclined relative to the axis of the flow duct or the pipe line. The inclination of the deflecting elements, which are lined up in rows, is in the same direction within a row and in opposite directions from row to row. Such a vortex element covers a single cohesive area, e.g. a circular or rectangular cross section. It serves to subject a flow of a medium through the pipe line or the flow duct to vorticity, as a result of which effective intermixing with a substance fed into the medium can be achieved. Comparable, large vortex elements are also described in European Patent 0 634 207 B1 and in International Publication No. WO 95/26226 A1. The main field of application of such vortex elements is the nitrous-oxide reduction of flue gas by the admixing of ammonia in flow ducts having a cross-sectional area of typically a few square meters.